Gfi1B binds Triad1 in yeast 2-hybrid assays. (A) Yeast 2-hybrid screen with the Gfi1B clone that interacts with Triad1 (aa 109–493) and not with the empty vector control on double histidine and adenine selection medium containing X-α-gal. (B) Gfi1B was cloned into pGBD and tested for interaction in the reciprocal experiment with full-length Triad1 or deletion constructs in pGAD. The C-terminal RING finger (RING2) of Triad1 was the smallest essential domain for Gfi1B interaction. Used Triad1 mutants either lack the entire TRIAD domain (ΔTRIAD), the N- or C-terminal RING finger (respectively, ΔRING1 and ΔRING2), the DRIL domain (ΔDRIL), or both C-terminal coiled-coil regions (ΔCC1 + 2).